The present invention relates to a dyed mixed fiber article composed of fiber dyeable with disperse dye (hereinafter referred to as xe2x80x9cdisperse dyeable fiber) and polyurethane fiber, and a method for fast-dyeing the mixed fiber article with disperse dye, more specifically to a dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber, which is excellent in color value and color fastness, and a method for fast-dyeing the mixed fiber article.
When a mixed fiber fabric composed of a disperse dyeable fiber, typically polyethylene terephthalate fiber, and a polyurethane fiber is dyed with disperse dye, there is a problem in that since the disperse dye is excessively adsorbed in the polyurethane fiber, the color fastness of the dyed mixed fiber fabric is significantly lowered. To solve this problem, it is necessary to remove the disperse dye excessively adsorbed in the polyurethane fiber by reduction clearing of the dyed fabric.
Since the disperse dye excessively adsorbed in the polyurethane fiber in the mixed fiber article is difficult to sufficiently remove therefrom by reduction clearing, however, it is impossible to obtain a dyed mixed fiber article satisfactory in color fastness. Particularly, a dyed mixed fiber fabric dyed with disperse dye is weak, in color fastness, to perspiration-alkali.
There has also been a problem in color fastness to dry cleaning of the dyed mixed fiber fabric. This is because a dry cleaning liquid becomes significantly dirty to reversely contaminate the white part of the fabric or other fibers. A cause of the contamination of the dry cleaning liquid is the disperse dye remaining in the polyurethane fiber, and the degree of contamination of the dry cleaning liquid is approximately proportional to the residual concentration of the disperse dye. For this reason, it is necessary to carry out reduction clearing of the dyed mixed fiber article dyed with disperse dye under severe conditions wherein the concentration of a reduction agent and an alkaline agent is higher than the ordinary level, for example, 10 g/l, and a treatment temperature is as high as 90xc2x0 C. to intensify the rinsing conditions. In a mixed fiber article such as a covering yarn having a high covering degree of polyurethane fiber, however, even if the reduction clearing condition becomes severe, it is impossible to remove the disperse dye in the polyurethane fiber to a satisfactory extent, and the color value of the disperse dyeable fiber is lowered to aggravate the shade variation in every dyeing batch.
To obviate such a problem, there may be a case wherein dyes easily decomposable by the alkali reduction clearing are used, such as heterocyclic azo type, condensation type or diester type disperse dyes. This is problematic, however, because it is difficult to obtain all colors with such dyes and the price of the dye is high. Also, since spandex is excessively deeply dyed, no improvement is seen in the mismatching and unevenness of color shades. Under the existing circumstances now stands, deep dyed articles of clothings having a, sufficient color fastness have not been obtained especially in the outer wears and inner wears (under wear).
Also, for the purpose of suppressing the adsorption of dye in spandex, disperse dyeable fiber is initially dyed and then mixed with non-dyed spandex to result in a mixed fiber fabric having a high color fastness.
In Japanese Examined Patent Publication (Kokoku) No. 62-38479, a method for improving a color fastness, especially that to laundering, is proposed wherein a mixed fiber article containing elastomeric polyester filament is dyed with disperse dye and then treated with an aqueous solution of tannic acid and tartar emetic, although it is irrelevant to a mixed fiber article containing elastomeric polyurethane fiber. However, there is a problem in that, since a large amount of disperse dye remains in the elastomeric polyester filament itself, a dry cleaning liquid is significantly contaminated therewith when the mixed fiber article is subjected to a dry cleaning. Also, color fastness to perspiration does not reach a satisfactory level.
Accordingly, at present, there is no superior mixed fiber fabric which is high in color fastness, low in contamination of dry cleaning liquid. Since disperse dye is excessively adsorbed in the polyurethane fiber in the mixed fiber fabric composed of fiber dyeable with disperse dye and polyurethane fiber, the color value of the disperse dyeable fiber becomes, lower to result in a product with a poor appearance.
An object of the present invention is to provide a dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber excellent in wet color fastness such as that to perspiration-alkali or to washing. Another object of the present invention is to provided a method for fast color dyeing a mixed fiber article composed of disperse dyeable fiber and polyurethane fiber with the disperse dye at a predetermined color density while suppressing the dyeing of the polyurethane fiber.
The present invention is a dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber, having a color fastness to a perspiration-alkali of grade 3or higher according to JIS L-0848-A Method and a surface color depth of 20 or less in term of color value L.
Preferably, the dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber further satisfies at least one of a color fastness to perspiration-alkali of grade 4 or higher according to JIS L-0848-A Method and a dry cleaning liquid contamination value of grade 3 or higher according to JIS L-0860-A Method.
If the dyed mixed fiber article according to the present invention has a perspiration-alkali of grade 4 or higher according to JIS L-0848-A Method, the disperse dyeable fiber forming the mixed fiber article is preferably dyed with heterocyclic azo type, condensation type or diester type disperse dyes.
A degree of color depth of the polyurethane fiber contained in the mixed fiber article is preferably 60 or less. Thus, it is possible to maintain a wet color fastness of grade 3 or higher even if the dyed fiber mixed article according to the present invention is a piece-dyed product dyed with disperse dye.
A ratio of the polyurethane fiber to the disperse dyeable fiber in the dyed mixed fiber article according to the present invention is generally 40% or less. The mixing ratio may be suitably selected in accordance with forms or uses of the mixed fiber article. The remaining component in the mixed fiber article, i.e., the disperse dyeable fiber, may be mixed with wool, cotton, silk, ramie, cuprammonium rayon, viscose rayon or others. In a composite article composed of disperse dye dyeable fiber and another fiber such as cellulose fiber which is not dyeable with disperse dye, two-bath dyeing may be adopted, wherein the method according to the present invention is applied when the disperse dyeable fiber is dyed, and then the cellulose fiber is dyed with a direct dye or a reactive dye.
Alternatively, a mixed fiber article may be initially dyed by the method according to the present invention, and then further dyed by one-bath dyeing or two-bath dyeing, whereby the dyed mixed fiber article excellent in color fastness according to the present invention is obtainable.
A mixed fiber article composed of disperse dyeable fiber and polyurethane fiber may of a yarn structure and a fabric structure.
Examples of the yarn structure include a so-called covering yarn in which a bare yarn of the polyurethane fiber (having a thickness of 10 to 500 dtex) is covered with the disperse dye dyeable fiber (single and double covering yarns), a twisted yarn, a core yarn, or an entangled yarn.
On the other hand, examples of the fabric structure include a knit fabric, a woven fabric, a non-woven fabric and a composite fabric thereof (such as a laminated fabric). Concretely, there is an on-machine mixed fiber fabric in which bare yarns or covering yarns of the polyurethane fiber are arranged in parallel or adjacent to yarns of the disperse dye dyeable fiber on a weaving or knitting machine (in a case of the bare yarns, while stretching the former twice to four times the original length during the knitting or weaving operation) to be mixed in one fabric.
The polyurethane fiber used in the present invention for producing a mixed fiber article may be suitably selected from a group of polyether type, polyurethane fiber composed of diol component of polyether diol such as polytetramethyleneglycol, diisocyanate component of aromatic diisocyanate such as 4,4xe2x80x2diphenylmethandiisocyanate, and diamine component such as ethylenediamine; and polyester type polyurethane fiber composed of diol component of polyester diol composed of polycaprolactone or polyester composed of adipic acid/1,6 hexanediol/neopentyl glycol, and a diisocyanate component of aromatic diisocyahate such as 4,4xe2x80x2diphenylmethane diisocyanate. If necessary, the polyurethane fiber may contains one kind or more of metallic oxide or metallic hydroxide such as magnesium oxide, zinc oxide, aluminum oxide, magnesium hydroxide, zinc hydroxide, aluminum hydroxide, or hydrotalcite type compounds as a chlorination water anti-deterioration agent, a content of which is preferably in a range between 0.1 and 6.0% by weight, together with another known stabilizing agent, ultraviolet absorbing agent of the like.
The polyurethane fiber may be suitably selected from a bright type having high luster and a semi-dull type having suppressed luster in accordance with the uses thereof.
In this regard, it should be noted that the object of the present invention would not be achievable by using elastomeric polyester ether fiber instead of the polyurethane fiber. As shown in Comparative Examples described later, when the polyester polyether elastomeric fiber was used instead of the polyether type polyurethane fiber and dyed in a dye bath containing tannic acid and polyvalent metallic compound, no effect is recognized for suppressing the adsorption of disperse dye into the polyester polyether elastomeric fiber, whereby the improvement in color fastness is not discernible.
The disperse dye dyeable fiber to be mixed with the polyurethane fiber in the present invention includes fibers of polyethylene terephthalate, polyoxyethylene benzoate, polybutylene terephthalate, polyttrimethylehe terephthalate, polyamide, polyacryl, polyvinyl alcohol, acetate or others, which are dyeable with disperse dye.
The single fiber thickness of the disperse dye dyeable fiber is preferably in a range from 0.1 to 6 dtex, more preferably 0.5 to 3 dtex, and a total thickness thereof is in a range from 10 to 340 detex, although it is not limited thereto. By using such a fiber, a fabric excellent in dyeability and touch is obtainable.
The disperse dye dyeable fiber may be either of a continuous filament shape or a short staple fiber shape, including those uniform or irregular in thickness in the lengthwise direction, the cross-sectional shape of which may be circular, triangular, polygonal, multi-lobal or indefinite, including an L-shape, a T-shape, a Y-shape, a W-shape, an octagonal lobal shape, a flat shape and a dog-bone shape. The fiber may be either solid or hollow. The fiber may be converted to a yarn form such as a spun yarn manufactured from a ring spinning frame or an open end spinning frame, a filament yarn having a single fiber thickness in a range from 0.1 to 6 dtex (including an ultra-fine, yarn), a soft or hard twisted yarn, a mixed fiber yarn, a false-twist textured yarn (including a draw-false twist textured yarn of POY) or an air jet textured yarn.
In this regard, the mixed fiber article referred to in the present invention may contain a natural fiber such as wool, cotton or silk, or an artificial fiber such as cuprammonium rayon, viscose rayon or polyamide through a fiber-mixing means, such as a mixed-spinning process (including a ciro-spun or a ciro-fil), an entanglement mixing process (wherein yarns having various shrinkages are mixed together), a mixed-twisting process, a composite false-twist process (including an elongation-difference-false-twist process) or a two-feed air jet texturing process.
In a mixed article wherein natural fiber, cellulose fiber or polyamide fiber is additionally mixed with the disperse dye dyeable fiber, a two-bath dyeing method is used wherein the method according to the present invention is applied when the disperse dye dyeable fiber is dyed with disperse dye, and thereafter, the natural fiber, cellulose fiber or polyamide fiber is dyed with dye usually used therefor. Alternatively, prior to dyeing the mixed fiber article, the method according to the present invention is preliminarily applied, then the additionally mixed cellulose fiber, or another, is dyed by a one-bath dyeing or a two-step one-bath dyeing method, resulting in the dyed mixed fiber article excellent in color fastness according to the present invention.
When the disperse dye dyeable fiber is polyester fiber, the polyester fiber may be a conventional one. However, if it is necessary to avoid the embrittlement of polyurethane fiber due to heat during the dyeing, which is particularly required in a product for an underwear or sportswear use, an easily-dyeable polyester fiber is preferably used.
The easily-dyeable polyester fiber is polyester fiber which exhibits a dye-adsorption degree of 80% or higher when dyed in a dye bath containing disperse dye C.I. Disperse Blue 56 (for example, Resoline Blue FBL (Distar Company; trade name)) of 3% omf, having a bath ratio of 50 and a pH of 6 (adjusted with acetic acid) and containing a dispersant (for example, Disper TL (Meise Kagakukogyo; trade name) of 1 g/l, at 100xc2x0 C. for 120 minutes. The dye-absorption degree is represented by the following equation (1):
Dye-adsorption degree (%)=[dye adsorbed into fiber (weight)/dye added to dye bath (weight)]xc3x97100
The easily-dyeable polyester fiber includes polyethylene terephthalate homopolymer fiber spun at a speed of 4000 m/min or higher and heat-treated at a temperature in a range from 220xc2x0 C. to 300xc2x0 C. with dry heat or at a temperature in a range from 180xc2x0 C. to 240xc2x0 C. with wet heat, or spin-takeup fiber spun at a speed of 6200 m/min or higher. Instead of the above-mentioned polyethylene terephthalate fiber, an easily-dyeable copolymerized polyester fiber spun at a high speed, which is linear polymer having a repeated unit of ethylene terephthalate and containing a third component such as isophthalic acid, sodium sulfonic isophthalate, polyethylene glycol, adipic acid or another, may be used. The polyester fiber may contain a delustering agent, a stabilizing agent, an antistatic agent or the like usually added to synthetic fiber.
Another example of an easily-dyeable polyester fiber is polytrimethylene terephthalate fiber. This fiber is a polyester fiber having a main repeated unit of trimethylene terephthalate unit wherein the trimethylene terephthalate unit is contained approximately 50 mol % or more, preferably 70 mol % or more, more preferably 80 mol %, most preferably 90 mol % or more. Accordingly, a total amount of the third component; i.e., the other acidic and/or glycolic component; is approximately 50 mol % or less, preferably 30 mol % or less, more preferably 20 mol % or less, most preferably 10 mol % or less.
The polytrimethylene terephthalate fiber may be produced by either a method wherein, after an undrawn yarn has been obtained at a takeup speed of approximately 1500 m/min, it is drawn at a draw ratio in a range from 2 to 3.5 times, a spin-draw method, wherein a spinning process is directly combined with a drawing process, or a spin-takeup method, wherein a yarn spun from a spinning machine is directly taken up at a high speed of 5000 m/min or more. The trimethylene terephthalate fiber may contain a delustering agent such as titanium, a stabilizing agent such as phosphoric acid, an ultraviolet absorbent such as derivative of hydoxybenzophenon, a crystal nucleus agent such as talc, a lubricant such as aerozil, an antioxidant, a flame retardant, an antistatic agent, pigment, a fluorescent whitening agent, an infrared absorbing agent, an anti-foaming agent or others.
In this regard, polytrimethylene terephthalate is synthesized from terephthalic acid or a functional derivative thereof and trimethylene glycol or a functional derivative thereof in the presence of a catalyst and in a suitable reactive condition. During this synthesizing process, one kind or more suitable third components are added to obtain copolymerized polyester. After a polyester other than polymethylene terephthalate, such as polyethylene terephthalate, or nylon has been synthesized separately from polytrimethylene terephthalate, they are blended with each other or compositely spun (to obtain a sheath-core type yarn or a side-by-side type yarn). The third component to be added thereto includes aliphatic dicarbonic acid (oxalic acid, adipic acid or the like), cycloaliphatic dicarbonic acid (cyclohexane dicarbonic acid or the like), aromatic dicarbonic acid (isophthalic acid, sodium sulfoisophthalic acid or the like), aliphatic glycol, (ethylene glycol, tetramethylene glycol, 1,2-propylene glycol, tetramethylene glycol or the like), cycloaliphatic glycol (cyclohexane dimethanol or the like), aliphatic glycol containing aromatic group (1,4-bis(xcex2-hydoxyethoxy) benzene or the like), polyether glycol (polyethylene glycol, polypropylene glycol or the like), aliphatic oxycarbonic acid (xcfx89-oxycapronic acid or the like) or aromatic oxycarbonic acid (P-oxybenzoic acid or the like). Also, compounds having one or three or more ester-forming functional groups (benzoic acid, glycerin or the like) may be used provided the polymer is maintained substantially in a linear range.
The dyed mixed fiber article according to the present invention includes all of fiber articles composed of the above-mentioned disperse dyeable fiber and polyurethane fiber mixed with each other through the above-mentioned mixing means, provided they have a predetermined color fastness.
That is, the dyed mixed fiber article of the present invention composed of disperse dye dyeable fiber and polyurethane fiber, having a color fastness to perspiration alkali of grade 3 or higher according to JIS L-0848-A Method and having a surface color density of 20 or less in term of color value L, can be obtained by dyeing a mixed fiber article composed of non-dyed disperse dye dyeable fiber and polyurethane fiber with disperse dye.
A dyed mixed fiber article of a desired color is obtainable by mixing a disperse dye dyeable fiber dyed in one color or a group thereof, each dyed in a different color and mixed with the other, is mixed with polyurethane fiber to result in the desired dyed mixed fiber article. Since the mixed fiber article is not dyed with disperse dye according to this method for preparing the dyed mixed fiber article, the urethane fiber in the mixed fiber article is not dyed or contaminated with disperse dye, whereby it is possible to easily prepare the dyed mixed fiber article having a color fastness to a perspiration-alkali solution of grade 3 or higher according to JIS L-0848-A Method. However, when the mixed fiber fabric is widely used in a field of outer wear, underwear or sportswear, wherein various colors are desired, this is disadvantageous in production cost. Also, there is a problem of xe2x80x9cgrinningxe2x80x9d wherein a white rubbery elastomeric fiber is visible in the fabric to degrade the same. On such a point of view, it is preferable to apply the dyeing method according to the present invention to a non-dyed mixed fiber article to obtain a dyed mixed fiber article.
To obtain a dyed mixed fiber article of the present invention by dyeing a non-dyed mixed fiber article with disperse dye, it is necessary to adopt a special method for preventing the polyurethane fiber in the mixed fiber article from being dyed with disperse dye.
The inventors of the present invention have found that, if the non-dyed mixed fiber article is treated with a polyvalent metallic compound and tannic acid prior to being dyed, or dyed in a dye bath containing a polyvalent metallic compound and tannic acid, the dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber excellent in color value and color fastness is obtainable because the adsorption of disperse dye into the polyurethane fiber in the mixed fiber article is significantly suppressed, while the disperse dyeable fiber is selectively dyed with the disperse dye.
As described above, in the non-dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber, the adsorption of disperse dye into the polyurethane fiber can be significantly suppressed during the dyeing with disperse dye, and the disperse dye adsorbed into the polyurethane fiber is easily removable therefrom during the reduction clearing after the dyeing. Conveniently, this function is exhibited irrespective of kinds of color value chemical structure of disperse dye widely used in practical dyeing.
Accordingly, the dyeing method according to the present invention allows the use of benzolic azo type disperse dye to obtain the fast color dyed article, which is inexpensive in cost, rich in color variation, convenient in use and capable of deep shade dyeing. The function of suppressing the adsorption of disperse dye into the polyurethane fiber is also exhibited in heterocyclic azo type, condensation type and diester type disperse dyes which are liable to be desorbed during the reduction-clearing process.
According to the dyeing method of the present invention, since the adsorption of disperse dye into polyurethane fiber can be significantly reduced, irrespective of structural types of the disperse dye, the removal of disperse dye adsorbed in the polyurethane fiber can be easily done during the reduction clearing process, which solves the problem of color fastness relating to the contamination of polyurethane fiber during the reduction clearing process.
According to the dyeing method of the present invention, the dyed mixed fiber article having a color fastness to perspiration-alkali and the contamination of dry cleaning liquid of grade 3or higher is obtainable even by using not only the conventional benzolic azo type disperse dye but also another type thereof. In addition, when disperse dye of a type easily hydrolyzed with alkali, such as heterocyclic azo type, condensation type or diester type disperse dye is used, the color fastness to a perspiration-alkali solution and the contamination of dry cleaning liquid are further improved to grade 4 or higher.
According to the present invention, it is possible to select a dye from a wider dye spectrum including azo type disperse dye, heterocyclic azo type, condensation type or diester type disperse dye for realizing a desired color fastness of the resultant dyed article.
While antimony type compound is preferably used as polyvalent metallic compound, another type, such as tin type, aluminum type, zinc type, barium type or bismuth type, each of which may be used alone or combined with others, maybe used. As the antimony type compound, ammonium tartrate, sodium antimonyl tartrate and potassium antimonyl tartrate is preferable. Of them, sodium antimonyl tartrate is most preferably used.
The amount of polyvalent metallic compound used is preferably in a range from 0.01 to 1.5% omf, more preferably from 0.02 to 0.5% omf. If the amount is less than the lower limit, the object of the present invention may not be achieved, while even if it exceeds the upper limit, further improvement is not expectable.
The tannic acid is that obtained from Japanese gall or gall, and the amount thereof is preferably in a range of 0.1 to 10% omf, more preferably from 0.2 to 5% omf as a product concentration. If the amount is less than the lower limit, the object of the present invention may not be achieved, while even if it exceeds the upper limit, further improvement is not expectable but is uneconomical in cost.
A ratio in amount between the polyvalent compound and the tannic acid is in a range from 1:1 to 1:40, preferably from 1:3 to 1:20, more preferably from 1:3 to 1:10.
In the above-mentioned pretreatment prior to dyeing, the mixed fiber article is preferably immersed in aqueous solution containing polyvalent metallic compound and tannic acid, wherein a treatment temperature is preferably, in a range from 40 to 130xc2x0 C., more preferably from 60 to 100xc2x0 C. and a treatment time is preferably in a range from 10 to 40 minutes. At this time, pH of the treatment solution is preferably adjusted to 3 through 5 with a pH adjuster.
The mixed fiber article thus pretreated is dyed with disperse dye under the conventional dyeing condition usually applied to polyester fiber or others. That is, a dye solution containing disperse dye, a level dyeing agent, a pH adjuster or others is used as a dye bath, and the dyeing operation is carried out at a dyeing temperature suitable for disperse dyeable fiber, for example, in a range from 100 to 135xc2x0 C. preferably from 100 to 130xc2x0 C. for a period in a range from 20 to 40 minutes.
The disperse dye may be one kind or a blend of several kinds so that desired color depth of achromatic or chromatic color is obtainable.
Disperse dye generally includes benzolic azo type disperse dye such as monoazo, disazo or naphthalene azo type disperse dye wherein a basic structure is 4-nitro-4xe2x80x2-aminoazobenzene, and nitro group, halogen atom or cyano group is introduced into positions 2 and 2, 6 of diazo component, and alkyl group, alcoxy group, halogen atom or acylamino group is introduced into positions 2xe2x80x2 or 2xe2x80x2, 5xe2x80x2 of a coupling component, and amino group of position 4xe2x80x2 is substituted with alkyl, hydroxyalkyl, alcoxyalkyl, cyanoalkyl, aryl or aralkyl group, which may be equally applied to the present invention. Other examples of the disperse dye are a heterocyclic azo type disperse dye in which heterocyclic compound is used in diazo component or coupling component, such as thiazole azo, benzothiazole azo, quinoline azo, pyridone azo, imidazole azo or thiophene azo type disperse dye; a condensation type disperse dye including quinoline type disperse dye such as C.I. Disperse Yellow-54, C.I. Disperse Yellow-64, a coumarin type disperse dye such as C.I. Disperse Yellow-82, anaminoketone type disperse dye such as C.I. Disperse Yellow-58, a benzodifuranon type disperse dye such as C.I. Disperse Red 356 or C.I. Disperse Red 367; and a diester type disperse dye having diester group in the chemical structure, such as C.I. Disperse Red 278.
The dyeing method in which polyvalent metallic compound and tannic acid are dissolved in an aqueous dye solution to form a dye bath is carried out under the conventional condition for dyeing polyester fiber, for example, at a temperature in a range from 100 to 135xc2x0 C., preferably from 100 to 130xc2x0 C.
The dyeing period is preferably in a range from 20 to 40 minutes in view of the embrittlement of polyurethane fiber and the production cost. The pH of the dye solution is preferably adjusted to 4 to 5 by adding a pH adjuster, such as acetic acid, thereto.
As a level dyeing agent used in this method, alkyl naphthalene type such as xcex2-naphthalene sulfonic acid formaldehyde condensate and polyalkyleneoxide addition product of polyvalent alcoholic fatty ester or sulfated product thereof are preferably used.
In the present invention, after the completion of the dyeing operation of the mixed fiber article, the reduction clearing is carried out under the existence of hot alkaline agent.
The treatment with a co-existence bath of tannic acid and polyvalent metallic compound used in the present invention is aimed at suppressing the adsorption of disperse dye into polyurethane fiber so that a larger amount of disperse dye is given to the disperse dyeable fiber. According to the present invention, not only the adsorption of disperse dye into polyurethane fiber is significantly suppressed, but also the disperse dye diffused into the polyurethane fiber is quickly decomposed by the reduction clearing carried out after the dyeing, and substantially completely removed from the polyurethane fiber. Thus, the degree of pigmentation of the polyurethane fiber in the dyed mixed fiber article composed of disperse dyeable fiber and polyurethane fiber is lowered to 60 or less which enhances the wet color fastness of dyed article and significantly reduces the contamination of dry cleaning liquid.
Piece dyeing of the mixed fiber article of the present invention enhances the adsorption of disperse dye into the disperse dye dyeable fiber to reduce the waste dye and prepare the dyed mixed fiber article excellent in color value and appearance. Further, the color variation in every dye batch is suppressed to improve the operating efficiency of the dyeing machine. Since only a small amount of disperse dye is adsorbed into the polyurethane fiber, it is sufficient that the concentration of a reducing agent and an alkaline agent is in a range from 1 to 2 g/l, and it is unnecessary to rise a treatment temperature, whereby there is no generation of color variation in every reduction clearing batch.
When the mixed fiber article composed of disperse, dye dyeable fiber and polyurethane fiber is a fabric, it is preferably dyed after being knitted or woven and subjected to a relaxation scouring. In such a case, the scouring is preferably carried out at a temperature in a range from 60 to 98xc2x0 C. while relaxing the fabric as much as possible, in view of facilitating the stretch recovery of the fabric. When a shape set is necessary prior to dyeing, the fabric is preferably preset at a temperature in a range from 170 to 200xc2x0 C. by dry heat, and after the reduction clearing, finished in a usual manner, after which the fabric is finally set at a temperature lower than the preset temperature by 10xc2x0 C. or more.
The predyeing treatment with the co-existence bath of tannic acid and polyvalent metallic compound is very effective when the mixed fiber article is composed of disperse dyeable fiber and natural fiber such as wool, cotton or silk, cuprammonium rayon, viscose rayon, or polyamide fiber, or when the article is piece-dyed or product-dyed. The effect for suppressing the dye adsorption into the polyurethane fiber during the dyeing of the pretreated article with disperse dye is inferior to that when tannic acid and polyvalent metallic compound co-exist with each other in the dye bath of disperse dye, although the color fastness of the dyed mixed fiber article is sufficient.